Solve 8x − 9 = 135

The solution of 8x − 9 = 135 is x = 18.

8x - 9 = 135\ \Rightarrow\ x = 18

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The lines y = 8x − 9 and y = 135 meet at x = 18. The solution of the equation is the x-coordinate of the point where the two sides are equal.

How to work it out

1
The goal is to get x alone. Undo the operations in the opposite order: first the subtraction, then the multiplication.
$8x - 9 = 135$
2
Add 9 to both sides:
$8x - 9 + 9 = 135 + 9 \ \Rightarrow\ 8x = 144$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{144}{8} \ \Rightarrow\ x = 18$
4
Check: put x = 18 back into the equation.
$8\cdot18 - 9 = 144 - 9 = 135 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 9 = 135\ \Rightarrow\ x = 18 \]
\[ 8x - 9 = 135 \]
\[ 8x - 9 + 9 = 135 + 9 \ \Rightarrow\ 8x = 144 \]
\[ \frac{8x}{8} = \frac{144}{8} \ \Rightarrow\ x = 18 \]
\[ 8\cdot18 - 9 = 144 - 9 = 135 \checkmark \]

Trying values of x in 8x − 9 = 135

x	8x − 9	Equals 135?
16	119	no
17	127	no
18	135	yes
19	143	no
20	151	no

Questions

What is x in 8x − 9 = 135?

The solution of 8x − 9 = 135 is x = 18.

How do you solve 8x − 9 = 135?

Add 9 to both sides to get 8x = 144, then divide both sides by 8 to get x = 18.

How do I check the answer?

Replace x by 18: 8(18) − 9 = 135, which is 135.

Solve 8x − 9 = 135

How to work it out

Trying values of x in 8x − 9 = 135

Questions

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